The goal of this project is to clarify the role of the anterior olfactory nucleus (AON), a secondary olfactory projection site, in odor-guided behavior. Anatomical and behavioral evidence in the literature suggests that the AON and pyriform cortex, the other secondary olfactory projection, may play separate roles in orientation to odor and identification of odor, respectively. In order to test this hypothesis, selective ablations of these anatomically distinct projections will be made in adult hamsters. The effects of each lesion on neuronal degeneration pattern and behavioral performance in odor discrimination and localization tasks will be compared in the same experimental subjects. Results should (1) clarify the anatomical connections of the AON and (2) test the differential functional roles of cortical and subcortical olfactory pathways.